Objective: Understanding Healthy Aging Processes: 14. Sensory and Motor Processing. This new investigator award centers on the above topic, as well as drawing on topic 16. Executive Function. Both topics call for the study of factors associated with normal and pathological aging. In this regard, persons with cognitive impairment with and without dementia have been shown to have a higher prevalence and more serious consequences of falls as compared to age-matched, healthy controls. This greater falls associated risk may be linked to early decline in higher level executive control and attention processes needed to reallocate and more effectively compensate for sensory losses and situational demands. Although a few studies have suggested balance in Alzheimer's (AD) patients under complex conditions (e.g., concurrent cognitive task) is seriously compromised, little is known about AD patients' ability to accomplish ambulation and other tasks simultaneously. This proposal will determine which aspects of executive control and attention are important to walking in more complex environments under divided attention conditions in healthy controls and patients with a range of cognitive impairment (i.e., patients with mild AD without extrapyramidal signs and Mild Cognitive Impairment [MCI] with and without executive function deficits). First, set shifting ability and it's relation to mobility will be explored in a complex walking task modeled after the Trail Making Test. Second, a two part study will investigate the extent of attention resources necessary for walking on a challenging walkway and wilt evaluate which specific areas of working memory and attention are required for such successful completion. The inclusion of MCI patients with differing patterns of cognitive deficits is a unique feature of this proposal as will aid in delineating the distinct contributions of executive control of attention and memory to walking performance. This proposal will allow the investigator, with the help of a well established interdisciplinary team including members of the departments of psychiatry, geriatric medicine, neurology, and bioengineering, to develop laboratory assessment techniques for evaluating factors underlying the increased falls risk in patients with cognitive impairment and dementia. Examining how different cognitive processes affect mobility will help to better understand the demands that everyday walking places on patients with cognitive impairment, as well as help develop early identification and intervention strategies for those individuals most at risk for falls.